Degradation of ethylbenzene by free and immobilized Pseudomonas fluorescens-CS2

Pseudomonas fluorescens-CS2 metabolized ethylbenzene as the sole source of carbon and energy. The involvement of catechol as the hydroxylated intermediate during the biodegradation of ethylbenzene was established by TLC, HPLC and enzyme analysis. The specific activity of Catechol 2,3-dioxygenase in the cell free extracts of P. fluorescens-CS2 was determined to be 0.428 μmoles min−1 mg−1 protein. An aqueous-organic, Two-Phase Batch Culture System (TPBCS) was developed to overcome inhibition due to higher substrate concentrations. In TPBCS, P. fluorescens-CS2 demonstrated ethylbenzene utilization up to 50 mM without substrate inhibition on inclusion of n-decanol as the second phase. The rate of ethylbenzene metabolism in TPBCS was found enhance by fivefold in comparison with single phase system. Alternatively the alginate, agar and polyacrylamide matrix immobilized P. fluorescens-CS2 cells efficiently degraded ethylebenzene with enhanced efficiency compared to free cell cultures in single and two-phase systems. The cells entrapped in ployacrylamide and alginate were found to be stable and degradation efficient for a period of 42 days where as agar-entrapped P. fluorescens was stable and efficient a period of 36 days. This demonstrates that alginate and polyacrylamide matrices are more promising as compared to agar for cell immobilization

Validation of Biometrical Principles for Genetic Enhancement of Chickpea (Cicer arietinum L.)

In the present investigation, the degree of heterosis for seed yield varied considerably. Parent such as ICC 7315, ICC 13124, ICC 15697 and ICC 6877 were good general combiners and could be of use in breeding for improved productivity in chickpea. The top three crosses viz., ICC 11944 x ICC 13124 (16.95), ICC 9137 xICC 13124 (16.63) and ICC 2507 x ICC 2072 (13.10) exhibited highly significant positive (specific combining ability) effect with high per se performance for seed yield/plant. This indicated that the heterotic performance of these hybrids were mainly due to additive gene action. Further, these crosses are having parents with good xgood general combiners. The high Holics effects in these crosses was mainly through additive x additive type of interaction causing heterosis. Hence, direct selection for higher values of seed yield can be made in the advanced generations of the heterotic crosses involving such parents, as a large portion of the total variation is a result of additive gene effects. Considering F2 performance of these hybrids, three of the six highly heterotic F1’s in high diversity group and high mean (ICC 6877 xICC 7315, ICC 6877 xICC 2072 and ICC 6877 x ICC 10755) followed by high coefficient of variation and range. The mean F2 values of these hybrids range from 25.6 to 37g, from 32.2 to 39.0% coefficient of variation and the higher value of range from 41.2 to 43 g/plant. While in case of medium diversity group, three hybrids (ICC 15697 xICC 7315, ICC 3776 xICC 7315 and ICC 3776 xICC 10755) showed relatively high mean values and higher coefficient of variation with reasonably high range of expression but these figures were lower than those of the hybrids in high diversity group. These facts indicate that parents with high diversity have a better chance of showing high heterosis and better performance

Genetic Divergence under Three Environments in a Minicore Collection of Chickpea (Cicer arietinum L.)

Two hundred and three germplasm lines of minicore collections obtained from ICRISAT, Hyderabad were evaluated for eight quantitative traits under three environments viz. E1 (rainfed 2004–05), E2 (rainfed 2005–06) and E3 (irrigated 2005–06). Mahalanobis' D2 statistic was applied. These genotypes were grouped into 20, 16 and 25 clusters in E1, E2 and E3, respectively. In the present study in all the three environments, the genotypes of different geographic origin were randomly distributed in the clusters. Thus, there is no parallelism between the genetic distance and geographical diversity. The formation of 16, 10 and 18 distinct solitary clusters in E1, E2 and E3, respectively may be due to intensive natural or human selection for diverse adaptive gene complex. The pairs of clusters revealing maximum genetic diversity were identifi ed for all the three environments. It has been suggested that for varietal improvement the hybridization among the genotypes of divergent clusters should be done rather than depending on those genotypes of the cluster having minimum divergence. Genotypes of cluster XIX (ICC13124) had the highest mean value for pod number and earliness in E1. In E2, the genotypes of cluster XV (ICC12654) and XVI (ICC9848) were superior in respect of plant height, pods/plant and 100 seedweight, respectively. In E3, the genotype of cluster XVI (ICC13124) had the highest mean value for seed yield. Cluster XXIII (ICC6279) had the early maturing genotype and cluster XVIII (ICC5879) was superior in respect of pod number and tertiary branches/plant and cluster V(ICC 6816), cluster XI (ICC10341 and cluster XIII (ICC5504) had the tall genotypes. Therefore, these genotypes may be involved in multiple crossing programme to recover transgressive segregate

Genetic variability studies in minicore collection of chickpea (Cicer arietinum L.) under different environments

The present investigation was carried out on chickpea germplasm lines representing minicore collection obtained from ICRISAT, Hyderabad (A.P) for assessing genetic variability under three environments. Considerably high variability was observed for most of the productivity related traits in E3 (irrigated 2005-06). Over all the environments, genotype ICC 6279 was found to be early flowering. For seed yield per plant, ICC 13124 was the only top yielder in all the three environments. The genotype ICC 13124 was found promising for earliness, large seed size and high yield per plant in all the environments suggesting that this accession is best suited for both rainfed and irrigated condition during the rabi season

Heterosis in relation to genetic divergence in minicore collections of Chickpea (Cicer arietinum L.)

Genetic analysis in chickpea using twelve lines belonging to high, medium and low diversity groups from different inter and intra cluster and four testers having high per se productivity was carried out to study heterosis in relation to genetic diversity for yield and yield attributes. Significant variation for all the characters was noticed except number of primary branches per plant among parents. Parents versus hybrid interaction effect was highly significant for all the characters. The hybrids ICC 6279 x ICC 13124, ICC 15697 x ICC 13124, ICC 6877 x ICC 7315 and ICC 6877 x ICC 10755 exhibited negative significant mid parent heterosis for earliness. Twenty seven hybrids showed positive significant mid parent heterosis for number of pods per plant and the magnitude of heterosis values was high with the highest value of 119.61 per cent. Nearly 85–90 per cent hybrids showed significant positive mid parent heterosis for seed weight. The degree of heterosis for seed yield varied considerably Out of 48 hybrids, 19 exhibited significant positive mid parent heterosis, whereas three exhibited significant positive heterosis over mid parent. The top three potential hybrids over mid parent were ICC 6877 x ICC 2072, ICC 2507 x ICC 2072 and ICC 6877 x ICC 7315. Study of relationship between divergence of the parents and heterosis in the hybrids revealed that the parents separated by D2 values of high to medium magnitude generally showed higher heterosis for different characters. This indicate the role of both heterosis and genetic diversity of parents in realizing higher yield in chickpea

Genetic Variability Studies in Minicore Collections of Chickpea (Cicer arietinum L.) under Different Environments

The present investigation was carried out on chickpea germplasm lines representing minicore collection obtained from ICRISAT, Patancheru (AP) for assessing genetic variability under three environments. Considerably high variability was observed for most of the productivity related traits in E3 (irrigated 2005–06). This was evidenced by high range of mean performance for different traits in E3 compared to E1 (rainfed 2004–05) and E2 (rainfed 2005–06). Moderately high heritability and genetic advance (GA) was observed for many productivity related traits under E3. The higher PCV, although, heritability was reduced or remained same as that under E2. These findings revealed the importance of productivity related traits giving more response under E3 than E1 and E2 for better expression for crop improvement in chickpea. Over three environments, genotype ICC 6279 was found to be early flowering irrespective of the environmental effect while ICC 1882 was found to be early flowering in E1 and E2 whereas ICC 13124 and ICC 6279 were early in flowering in both E2 and E3 compared to early flowering check JGK-1. For seed yield/plant, 24, 22 and 17 genotypes showed significantly higher yield over check A-1 in E1, E2 and E3, respectively. Out of these, ICC 13124 (31.25 g, 32.85 g and 32.95 g) is the only top yielder in all the three environments. While genotypes ICC 6279 (28.9 and 27.85 g), ICC 13892 (30.05 g and 27.65 g) and ICC 13187 (27.45 g and 36.55 g) were top yielders in both E1 and E2 and ICC 12866 (27.65 and 40.15 g) and ICC 4533 (29.38 and 38.8) were identified as top yielders in E2 and E3, while ICC 12947 (27.9 g and 40.9 g) and ICC 6877 (18 g and 35.33 g) were top yielders in E1 and E3, respectively. On overall basis, the genotype ICC 13124 was found promising for earliness, large seed size and high yield/plant in all the environments suggesting that this accession is best suited for both rainfed and irrigated condition during the rabi season

Characterization of drought tolerant accessions identified from the minicore of chickpea (Cicer arietinum L.)

Terminal drought is one of the major causes of yield losses in chickpea (Cicer arietinum L.) and there is scope for recovery of major part of this loss through genetic improvement. The progress in breeding for drought tolerance is slow due to the quantitative and temporal variability of available moisture across years and the low genotypic variance in yield under drought. Deep and prolific root system is a high priority trait that can improve drought tolerance in chickpea.Ten accessions which were identified as drought tolerant based on drought susceptible index (DSI) and drought tolerant efficiency per cent (DTE%) were evaluated during rabi 2006–07 along with stanadred check Annigeri-1 and drought tolerant checks ICC 4958 and ICC 10448 under irrigated and rainfed condition for seed yield and root traits. Wide range of genetic variability, moderate to high heritability and high genetic advance for yield and its component traits was observed in drought tolerant accessions evaluated under moisture stress and irrigated situations during 2006–07. Among the drought tolerant genotypes evaluated, ICC 13124 showed maximum yield levels under irrigated (1220 kg/ha) as well as rainfed condition (990 kg/ha). The per cent reduction in yield was minimum (18.9%) as compared to checks under moisture stress for this genotype. Observations on root length, root weight and root volume showed that ICC 13124 was equally good in respect of root traits which can be used in the breeding programme aimed at drought tolerance

Inheritance of field resistance to sorghum charcoal rot and selection for multiple disease resistance

Six segregating and nonsegregating generations of three R x S and two S x S crosses were studied for charcoal rot resistance under epiphytotic conditions. CSV-5 (148/168) was comparatively the most resistant parent. The F1 showed partial dominance of resistance. The resistance appears to be a polygenic threshold character governed by duplicate epistasis with low heritability (38%). The F3 progenies transgress the parental limits. In absence of absolute resistance for charcoal rot, selection 2 S.D. below population mean (S.I. = 1%) results in selecting resistant transgressive segregates. Charcoal rot, SDM and leaf rust inherit independently. It is possible to combine these characters through simultaneous selection by choosing rust resistant plants from the segregating F3 progenies possessing <1% SDM and <10% charcoal rot susceptibilit

Inheritance of field resistance to sorghum downy mildew

Inheritance of SDM resistance was studied in a set of resistant x susceptible crosses using both quantitative and quantitative genetic analysis techninues. Segregatiod ratios in the (R x S) crosses clearly indicated the presence of three gene pairs which exhibited both complementary and duplicator types of gene interaction among them. Quantitive genetic analysis of this character indicated similar results. SDM resistance was observed to be quantitive threshold characte

Exploiting genomic resources for efficient conservation and utilization of chickpea, groundnut, and pigeonpea collections for crop improvement

Both chickpea and pigeonpea are important dietary source of protein, while groundnut is one of the major oil crops. Globally, ~1.1 million grain legume accessions are conserved in genebanks, of which, ICRISAT genebank holds ~50,000 accessions of cultivated species and wild relatives of chickpea, pigeonpea, and groundnut from 133 countries. These genetic resources are reservoirs of many useful genes for the present and future crop improvement programs. Representative subsets in the form of core and mini core collections have been used to identify trait-specific genetically diverse germplasm for use in breeding and genomic studies in these crops. Chickpea, groundnut and pigeonpea have moved from ‘orphan’ to ‘genomic resources rich crops’. The chickpea and pigeonpea genomes have been decoded, and the sequences of groundnut genome will soon be available. With the availability of these genomic resources, the germplasm curators, breeders and molecular biologists will have abundant opportunities to enhance the efficiency of genebank operations, mine allelic variations in germplasm collection, identify genetically diverse germplasm with beneficial traits, broaden the cultigen’s genepool, and accelerate the cultivar development to address new challenges to production, particularly with respect to climate change and variability. Marker-assisted breeding approaches have already been initiated for some traits in chickpea and groundnut, which should lead to enhanced efficiency and efficacy of crop improvement. Resistance to some pests and diseases has been successfully transferred from wild relatives to cultivated species